Radiologia Brasileira - Publicação Científica Oficial do Colégio Brasileiro de Radiologia

A NEW PROPOSAL FOR MONITORING PATIENTS IN NUCLEAR MEDICINE.

J. Willegaignon; Maria I.C. Guimarães; Marcelo Tatit Sapienza; Michael G. Stabin; Luiz F. Malvestiti; Marília Marone; Gian-Maria A.A. Sordi.

Instituto de Pesquisas Energéticas e Nucleares (IPEN); Centro de Medicina Nuclear da Faculdade de Medicina da USP; Hospital Samaritano; Universidade de Vanderbilt.

The measurement of the exposure rates is fundamentally important in the release of patients given radioactive material and for keeping the exposures of others as low as reasonable achievable (ALARA). Similar measurements methodologies have generally been used for point and extended sources, but this approach may lead to methodological errors in calculating radiation dose estimates. In this study, nuclear medicine patients (n=122) who received activities of Na131I for therapy (0.74 to 16.6 GBq, 20 to 450 mCi) were monitored using different measurement methodologies and the results showed that the usual measurement performed at 1.0 meter in front of the body resulted in a mean error of 40% between experimental and theoretical exposure rates. The best measurements were obtained when performed at 2.0 meters in front of the patients. With this approach, the error was about 2% between experimental and theoretical values and the determination of the activity retained by patients’ body yield more accuracy and precision following the measures at 2.0 meters instead 1.0 meter. These findings suggest a new methodology for patients’ measurement in nuclear medicine and could be useful for personal monitoring in cases of radiological emergencies involving 131I ingestion.

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EVALUATION OF THE ABSORBED DOSE FROM PATIENTS BASED ON WHOLE-BODY 131I CLEARANCE IN THYROID CANCER THERAPY.

J. Willegaignon; Michael G. Stabin; Maria I. C. Guimarães; Luiz F. Malvestiti; Marcelo Tatit Sapienza; Marília Marone; Gian-Maria A.A. Sordi.

Instituto de Pesquisas Energéticas e Nucleares (IPEN); Centro de Medicina Nuclear da Faculdade de Medicina da USP; Hospital Samaritano; Universidade de Vanderbilt.

The evaluation of the absorbed dose from radioactive patients during the treatment of thyroid disease is an important factor to establish precautions in these procedures, and the 131I retention/excretion by patients’ body provides additional information to medical and radioprotection service. In 94 patients, the measurement of the exposure rates was performed over the 7 days after Na131I administration and the rates permitted to study the dynamic of excretion and the potential dose evaluation. The administered activities ranged from 3.7 GBq (100 mCi) to 16.65 GBq (450 mCi) and the results proved that the majority of the activity is excreted by patients in first three days after Na131I administration. The average 131I activity excreted at 24, 48, 72, 96 and 120 hours after oral administration was (72 ± 10), (91 ± 6), (97 ± 3), (98.9 ± 1.5) and (99.6 ± 0.7)% respectively. According to the administered activity, the evaluation of the accumulated absorbed dose from patients ranged from 3.0 ± 0.7 to 8.4 ± 1.1 mSv at one meter and 1.2 ± 0.4 to 3.2 ± 0.4 mSv at two meters. The data reported here are important to radioprotection policy and to add and improve on the guidelines reported in USNRC Regulatory Guide 8.39.

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SCHISTOSOMIASIS HAEMATOBIA: CLINICAL ASPECTS AND SCINTIGRAPHIC IMAGES IN BRAZILIAN PATIENTS.

Joaquim d’Almeida; Carmelindo Maliska; Paulo M. Pellegrini; Rodrigo A. Collares; Maria E. Penas; Maria G.A. Cruz.

Serviço de Medicina Nuclear do Hospital Central do Exército, Triagem – Rio de Janeiro, RJ, Brasil.

The Schistosoma haematobium is a trematode that cause schistosomiasis haematobia and resides in venous plexus around the vesicle bladder, where the eggs are deposited. The aim of this study was to evaluate the scintigraphic alterations trying to identify obstructive uropathy and its modifications during clinical evolution, because the worsening of renal function is related to the intensity and duration of the obstruction. In this study, 19 male Brazilian patients aged from 26 to 36 years, infected in Mozambique, were evaluated. Clinical and laboratorial diagnosis was done in a period of few months to 7 years after the contact with parasite. They underwent dynamic renal scintigraphy with 99mTc-DTPA and tubular function with 99mTc-DMSA. Among results there were 2 patients had abnormal scintigraphy 12 months after beginning of symptoms. Other 2 patients had normal exams 24 months after being symptomatic. Among patients being symptomatic for 48 months only one had obstructive pattern and renal scar, two had obstructive pattern and one presented a normal exam. We can be concluded that the alterations are randomic in relation to duration of symptoms, depending more on individual response, parasite charge, then others. This favors the idea of close clinical and scintygraphic evolution because alterations non-detected earlier increases morbidity and irreversible damage to patient.